The invention relates to marine drive units, and more particularly to improvements affording reduced drag.
A marine drive includes a lower drive unit near of the transom of a boat and having a vertical depending strut portion with at least one vertical drive shaft and having a lower horizontal torpedo portion with at least one horizontal propeller shaft carrying at least one rear propeller.
The present invention provides improvements in the blending or fairing between the strut and torpedo shapes to optimize the upper surface piercing shape and the lower submerged shape in combination. In accordance with the invention, drag is reduced by eliminating concave outer surface profiles in horizontal cross-sections through the blended portion between the strut portion and the torpedo portion. In the preferred embodiment, all horizontal cross-sections through such blended portion have outer surface profiles which are continuously curved convexly along the entire front to back length thereof. Vertical cross-sections have central zones of concave outer surface profiles whose degree of concave curvature continually increases front to back such that the largest radius of such concave curvature along the vertical cross-section outer profile is at the front of the blended portion.